This invention relates to foam blowing agent blends of (a) 1,1-dichloroethane (xe2x80x9cD11xe2x80x9d) with (b) n-pentane (xe2x80x9cn-C5xe2x80x9d), i-pentane (xe2x80x9ci-C5xe2x80x9d), cyclopentane (c-C5) or an i-C5/c-C5mixture, and to polyol premixes containing such blends. The foam blowing agent blends are particularly useful for making closed cell polymer (insulation) foams having improved fire resistance, such as polystyrene, phenolic and polyurethane foams.
Chlorofluorocarbons (xe2x80x9cCFCsxe2x80x9d) had been used as blowing agents for rigid, closed cell insulation foams for many years because they offer outstanding fire resistance in addition to good thermal insulation. However, CFCs have been phased out because they are said to be detrimental to the ozone layer. Zero ozone depletion alternatives such as pentanes have been identified, but pentanes are highly flammable and their resulting foams suffer undesirable fire performance properties. It is increasingly difficult for pentane blown foams to meet stringent fire performance requirements, so that yet another alternative with better fire resistance performance is desirable.
Foam blowing agent compositions are provided, which compositions comprise D11 and a pentane selected from the group consisting of n-C5, i-C5, c-C5 and an i-C5/c-C5 mixture (preferably as an equimolar mixture), as well as foam premix compositions comprising a polyol and the blowing agent composition.